This application has two major goals. The first is to extend follow-up in the Michigan Bone Health Study (MBHS) population for an additional 4 annual examinations. The 10-year MBHS longitudinal study, initiated in 1992, has characterized the natural history of musculoskeletal status and its alteration among women (aged 25-45 at their baseline) whose hormone status is changing because of menopause and obesity. Secondly, we propose to evaluate the influence of the metabolic environment generated by obesity on musculoskeletal status and physical functioning with a focus on oxidative stress and inflammation. The aims are to: A) Describe the 13-year rate of change in body composition and the following: 1) rate of pre, perimenopausal and postmenopausal bone loss including bone mineral density (BMD), bone width, and bone mineral concentration, 2) incidence and prevalence of OAK, and 3) change in physical functioning. B) Describe changes in ovarian (i.e.. estradiol') and non-ovarian hormone concentrations (i.e., androstenedione) over a 13-year period and relate the hormone changes to 1) rate of pre, perimenopausal and postmenopausal bone loss, 2) incidence and prevalence of OAK, and 3) change in physical functioning in mid-aged women. C) Evaluate the potential mechanisms for the impact of change in fat and lean mass by assessing whether an exaggerated inflammatory state coupled with increasingly greater insulin resistance (seen in obesity) increases the likelihood of greater BMD loss, OA progression, and greater physical limitation. Data has been collected annually from the 604 enrollees of MBHS ten times over the period 1992/93 to 2002/3 and excluding 1996/1997. More than 60% of the study population has been assessed at all ten evaluations and 84% of the population had at least eight (8) of the ten (10) evaluations. Results related to the three major outcomes have been presented in more than 30 publications. The proposed 4 additional yearly assessments will cover a 13-year period that includes the reproductive life span of women to the postmenopause. Annual assessments will include BMD, measures of physical functioning, phlebotomy and urine collection to allow assessment of hormones and inflammation markers. X-rays will be taken in the 2nd-3nd year of the proposed time period to have a series of 4 hand and knee films over the time interval of interest. Stored specimens (serum and urine) will be assayed to have alternative year measures of selected hormones, inflammation markers, glucose and insulin over the 13-year period. This study will provide a unique setting to evaluate the impact of an aging related process (menopause) and an environmentally related process (increasing obesity) on the development and progression of musculoskeletal disease and their potential for contributing to degree of functioning.